Synthesis and Catalytic Properties of Nanoparticulate Intermetallic Ga-Pd Compounds

A two-step synthesis for the preparation of single-phase and nanoparticulate GaPd and GaPd2 by coreduction of ionic metal-precursors with LiHBEt3 in THF without additional stabilizers is described. The coreduction leads initially to the formation of Pd nanop articles followed by a Pd-mediated reduction of Ga3+ on their surfaces, requiring an additional annealing step. The majority of the intermetallic particles have diameters of 3 and 7 nm for GaPd and GaPd2, respectively, and unexpected narrow size distributions as determined by disk centrifuge measurements. The nanoparticles have been characterized by XRD, TEM, and chemical analysis to ensure the formation of the intermetallic compounds. Unsupported nanoparticles possess high catalytic activity while maintaining the excellent selectivity of the ground bulk materials in the semihydrogenation of acetylene. The activity could be further increased by depositing the particles on alpha-Al2O3.